Sedimentation tank



Dec. 22, 1942.

C. H. SCOTT SEDIMENTATION TANK Filed June 24, 1941 4 Sheets-She et 1 ATTORNEY.

'Dec. 22, 1942. c. H. SCOTT SEDIMENTATION TANK Filed June 24, 1941 4 Sheets-Sheet s INVENTOR.

BY cm fizasmacorr,

ATTOFA/f).

Dec. 22, 1942.

C. H. SCOTT SEDIMENTATION TANK Filed June 24, 1941 D 4 Sheets-Sheet 4 CHAR/.55 h. 5w

ATTORNEY Patented Dec. 22, 1942 SEDIMENTATION TANK Charles H. Scott, Westport, Conn, assignor to The Dorr Company, Inc., New York, N. Y., a. corporation of Delaware Application June 24, 1941, Serial No. 399,447

9 Claims.

- and it can be defined as the generated movement described by a point on an arm (herein to be called the secondary arm) that rotates about a point on another rotating arm (herein to be called the primary arm), the sense of rotation of each arm to be opposite to that of the other, and

the rate of rotation of the primary arm being three times that of the secondary arm, if an equilateral quadrangle is to be generated.

It is among the objects of this invention to provide a mechanism of this class, that is particularly effective as to its sediment collecting capacity and stable and positive in operation, that is furthermore compact, has a low headroom requirement, and is simple, and rugged in construction; as well as to provide a generating mechanism that is mecham'cally eificient.

Still another object is that the sludge raking mechanism should have no submerged bearings.

In order to attain some of these objects, there is provided an epicycloidally rotating sediment raking structure or member that is provided with A single blade sediment impelling convolute arms. Due to the character of the kinematics of the epicycloidal movement, these arms perform a predominantly radial or longitudinal component movement during that part of their rotation when they move into or explore the corner portions of the settling area, by virtue of which longitudinal component movement the arm or blade may be said to slice through the sedimented matter. However, during another phase of their rotation the arms perform a predominantly transverse progressive component movement whereby the blade or arm may be said to exercise a bulldozing action upon the sediment. The

resultant effect of the alternate slicing and bulldozing action of the arms or blades is that the bulk of the sediment is conveyed along the shortest possible path towards a point of withdrawal at the center of rotation.

According to one feature the epicycloidally rotating sediment raking structure is driven by a mechanism that is supported by a pier. The drive mechanism and the raking structure are thus substantially sustained upon the pier. The sediment raking structure comprises a cage surrounding the pier, and a sediment collecting arm or blade of convolute shape connected with the cage at the bottom thereof and effective to move the sediment along the shortest possible path towards a centrally located outlet.

The invention possesses other objects and features of advantage, some of which, with the foregoing, will be set forth in the following description. In the following description and in the claims, parts will be identified by specific names for convenience, but they are intended to be as generic in their application to similar parts as the art will permit. In the accompanying drawings there has been illustrated the best embodiment of the invention known to me, but such embodiment is to be regarded as typical only of many possible embodiments, and the invention is not to be limited thereto.

The novel features considered characteristic of my invention are set forth with particularity in the appended claims. The invention itself, however, both as to its organization and its method of operation, together with additional objects and advantages thereof, will best be understood from the following description of a specific embodiment when read in connection with the accompanying drawings in which:

Fig. 1 is the plan view of a clarifier or settling tank of square settling area, and equipped with a three-arm sediment collecting structure, the arms being of the convolute type, moving in epicycloidal fashion.

Fig. 2 is an elevational section of the clarifier, taken on the line 2-4, of Fig. 1.

Fig. 3 is an enlarged detailed view, along the line 33 in Fig. 1, of the epicycloidal drive mechanism that is mounted upon the center pier and in turn supports the sediment collecting structure.

Fig. 4 is a part-sectional plan view of the structure shown in Fig. 3.

Fig. 5 is a perspective detailed view of the three-armed sediment collecting structure, including a cage construction whereby it can be mounted on and surrounds the epicycloidal drive mechanism and the center pier.

Fig. 6- is a diagrammatic showing of the various operating positions with respect to the tank of the three-armed sediment collecting structure.

Fig. 7 is an enlarged view of the drive mechasect portion 323 that continues nism shown in Figure 3 with parts drawn apart. A square settling tank having sediment collecting mechanism embodying the invention is shown in Figs. 1 and 2. The tank has a fiat horizontally extending bottom portion i0, sidewalls H and I2, an inlet end or wall 13 with influent channel therealong, and an efliuent end or wall i5 with an overflow weir 15ahaving an efiiuent channel 6 extending therealong. A sump lfia for the discharge of collected sediment is disposed at the foot of the pier H disposed in the center of the tank. Upon the pier I1 and selfsustained thereon is supported a sediment collecting structure I8 and a drive mechanism l9 therefor. The outline of the flat or horizontally extending bottom portion I3 is substantially a square, having rounded corners defined by the radius R. The corner portions of the walls of the tank form corner spaces between them and the corner curve as defined by the radius R. These corner spaces lying outwardly beyond the corner curve of the flat bottom portion l0 and defined by the radius R, are not being reached by sediment collecting corner exploring arms or blades hereinafter described, and therefore the bottom corners of these corner spaces are shown to be occupied by fillets F, which offer a downward sloping face extending from the inner faces of the corner portions of the walls downwardly so as to interwith the fiat bottom portion l0 along the curved line defined by the radius R. These fillets F prevent settling matter from collecting in the corner spaces of the tank that are not being reached by the sediment collecting mechanism, causing that matter to slide down the sloping face of the fillets F on to the horizontal bottom portion ID, where the matter is collected by the sediment conveying arms or blades of the mechanism hereinafter described.

A perspective view of the sediment collecting structure or member I8 is shown in the Fig. 5. This member is a rigid three-armed unit, having three convolute arms 20, 2|, 22, the rear end of each arm being fastened as by gusset plates to a portion of the preceding arm, that is to a point intermediate the ends thereof. For example, the rear end of arm 20 is fastened to the arm 22, as by gusset plate 23. Each of the arms 20, 2!, 22, is in turn fixed to an annular structure 24, as by gusset plates 25. A cage rigidly rising from the annular structure 24 is desig- .nated by the numeral 23 and comprises three angular members 21, 28, 29, radially disposed and one-hundred-twenty degrees apart from one another, the inner ends of the angular members being rigidly interconnected at a central junction as indicated by a gusset plate 30 in Fig. 5. The junction of the three members in effect forms a hub portion which has rigid and concentric therewith on the underside a gear 3| which constitutes part of the epicycloidal mechanism presently to be described.

On the top of the pier i1 is mounted a hollow frame 32 comprising a lower frame or body portion 32a, and an upper frame or cover portion 3217. Both frame portions 32a and 321) have provided in them bearings for the gearing means hereinafter to be described. The lower frame portion 3211 has a bottom pocket 32c comprising a horizontally extending bottom portion 32d and vertical wall portions 32c. The pocket 320 is formed in part by an overhanging horizontal horizontally beyond of the pocket, thereby form- 32g that surrounds and exthe wall portions 320 ing a bottom portion tends from the upper end of the wall portions 32a of the pocket 320. The bottom portion 32g is shown to be slightly dished or tray-shaped and to terminate in a flange 32h for connection with the upper frame portion 32b. The bottom portion 32g of the lower frame portion 32a, has a downwardly and circumferentially extending foot portion 32p merging into the walls of the pocket 320 (in a manner not especially shown), and terminates in a flange 32g having a lower face 32r whereby the frame 32 and thereby the entire sediment raking mechanism is supported upon the pier i! by way of anchor or fastening means not particularly shown. The upper frame portion 321) comprises a horizontally extending top portion 321' having downwardly extending marginally extending wall portions 32k terminating in a flange 32Z that matches the flange 32h of the lower frame portion 32a and is fastened thereto by suitable connecting means, for instance bolt and nut connections not shown. The top portion 322 of the upper frame portion 32b is shown to have an opening 32m, and it also has a centrally disposed hub portion 3212 extending upwardly therefrom. The hollow frame 32 just described houses a drive motor 33, and various gears constituting part of an epicycloidal gear drive. The motor 33 has a vertical axis of rotation and a pinion 34 meshing with a larger gear 35 for speed reduction. The gear 35 is fixed to the lower end of a vertical shaft 38 having a vertical thrust bearing 31 in the overhanging portion 32) of the pocket 320 in the lower frame portion 32a. The intermediate portion of the shaft 36 has a guide bearing 31a inside and by way of the hub portion 3211 of the upper frame portion 3212. A small gear 38 is fixed upon the vertical shaft 36 and disposed intermediate the thrust bearing 31 in the overhanging portion 32 of pocket 32c and the top portion 321 of the upper frame portion 32b. Another small gear 38a is fixed on the upper free end of the vertical shaft 36 and disposed above the hub portion 3211. of the upper frame 32b, and. it meshes with the gear 3| above mentioned as being fixed to the sediment collecting member I8. The small gear 38 meshes with a larger gear 38 fixed on a vertical shaft or counter-shaft 40 having a vertical thrust bearing 4| in the bottom portion 32g of the lower frame 32a, and upwardly spaced therefrom a guide bearing 42 in the top portion 322' of the upper frame portion 32b, the gear 39 thus being disposed intermediate the two bearings 4| and 42. The upper free end of the countershaft 40 has fixed thereto a small gear 43 disposed above the top portion 32b of the upper frame portion 321', the gear 43 in turn meshing with a larger gear 44 rotatable upon and about the hub portion 32n of the upper frame 32b.

It will now be understood that the hub por-- tion 3211 of the frame 32 serves as a dual bearing, namely, for the vertical shaft 36 within it, and for the gear 44 surrounding it.

It should be noted that the gear 44 is connected with and causes the rotation of an arm or crank arm 45, the effective length of which is herein designated by the letter L, the gear 44 being connected with the arm 45 by bolts 45a. A bushing 45b is shown to be provided in the hub portion of the gear 44, whereby the gear 44 is rotatably fitted over the stationary hub portion 3211 of the upper frame portion 32b. The arm 45 has an annular bearing 450 at its center of rotation upon the top portion 322' of the upper frame 32b, and mounted on the outer end of the arm at the underside thereof are a pair of conical supporting rollers 46 and 41 operating upon a track 48 provided on top of the upper frame portion 32b of the hollow frame 32. These rollers and the track, as will be seen, sustain the weight of the sediment collecting structure or member I8. The arm incidentally is unitary with a rotary cover 49 overlying the gears 43 and 44 as well as the track 48. The arm 45 constitutes what is herein called the primary arm of the epicycloidal drive mechanism, and it rotates about what is herein called the primary vertical axis. The sediment collecting structure or member 8 is mounted upon the primary arm 45 to rotate in epicycloidal fashion i about a secondary vertical axis which is spaced from the primary axis. It will be understood that the sediment collecting structure or epicycloidally rotating member l8 comprises a cage structure in the form of the members 27, 28, 29 surrounding the pier H, and the convolute sediment raking members 20, 2|, 22 extending horizontally from the lower end portion of the cage structure. It will also be noted that the sediment collecting structure I 8 is fastened to the v gear 3| as by means of bolts Mia. The outer end of the primary arm 45 is provided with a vertical bearing for supporting the sediment collecting member l8. In the present embodiment this bearing is shown to be represented by a vertical pivot 5| fixed in a hub portion 5|a provided at the outer end of the arm, and a thrust bearing 52 and a guide bearing 53 surrounding the pivot.

The rotary cover 49 is formed with a hub portion 490. into which also extends and fits the bushing 45b, since it will be remembered that the rotary cover 49 is unitary and connected with the gear 44 by means of the bolts 45b. A pan 54 interconnects the hub portions 49a and 5|a of the arm 45, and together with an annular cover plate it houses the gears 3| and 38a.

The arm or arms of the sediment collecting structure l8 constitute what may herein collectively be called the secondary arm of the kinematic or epicycloidal system underlying this construction.

An apron 56 is shown to extend downwardly from the rotary cover 49 of the primary arm 45, and to partly surround the pier I7, and to extend substantially to the bottom of the tank. The lower end of the apron 56 carries auxiliary sediment engaging blades or scrapers 51 to aid in disposing of the sediment that is brought into the region of the discharge sump 16a by the sediment collecting convolute arms 20, 2|, 22. As will be explained hereinafter the auxiliary blades 51 move counter-clockwise and at three times the speed of the rake arms moving clock- Wise.

Operation In order to cause the sediment collecting structure It to perform its epicycloidal movement in the clockwise direction of arrow 53 (see Fig. 1), the motor pinion 34 (see Fig. 4) must drive the gear 35 in counter-clockwise direction as indicated by arrow 59, consequently driving the gears 38 and 33a in the same direction as shown by arrows 50 and 6| respectively, inasmuch as all three gears 35, 38, 38a are fixedly mount-ed on the same vertical shaft.

It will then be seen that the gear 38 rotates the larger gear 39 and thereby the countershaft 49 in clockwise direction as indicated by arrow Ill 6 2, while the gear 38a rotates the large gear 3| also in clockwise direction as indicated by arrow 63 (see Fig. 4). As a result the arm 45 will rotate counter-clockwise in the direction of arrow 64, while the sediment collecting strucr ture l8, in other words, the sediment raking arms 20, 2|, 22 will rotate clockwise in the direction of arrow 58.

In order that the sediment raking arms should work over a substantially square sedimentation area having straight sides and rounded corners, the length L of the arm or crank arm 45 should be approximately 7% of the width of the settling area. For instance, if the settling area is ft. square, the effective length L of the crank arm 45 should be 7 ft. This ratio might vary slightly, but for practical purposes should substantially vary not more than 5%, in other words, the crank arm length in the above eX- ample should, for instance, not be less than 6.65 and not more than 7.35 feet.

For a square tank the gear ratios in the drive mechanism must be such as to produce /3 of a revolution of a rake arm clockwise for one full revolution of the crank arm 45 counter-clockwise. For this purpose the gear ratios may be as follows:

Gear 3| :gear 38a=6 1 Gear 35 gear 38 :3 :1 Gear 44 1 gear 43 :3 1

On the basis of these gear ratios the shaft 36 and hence the gears 38 and 38a will make 9 revolutions counter-clockwise, as the crank arm 45 makes revolution counter-clockwise. Accordingly, the

ear 3| with the sediment raking arms 20, 2|, 22 will rotate revolution counter-clockwise, that is at one-ninth of the speed of gear 38. If it were assumed that the primary or crank arm 45 did not rotate, gear 3| would be driven calm revolutions clockwise for every 9 revolutions counter-clockwise of gear 38 or 33a.

In fact, however, the arm 45 rotates one revolution counter-clockwise for every 9 revolutions of gear 38a, and carries gear 3| with it. That is to say, for every 9 revolutions of gear 3811 one revolution is last in relation to gear 3! making the rotation of the latter revolutions clockwise in relation to arm 45. Accordingly, as arm 45 rotates one revolution counter-clockwise for every 9 revolutions of gear 38a, gear 3| with the sediment raking arms 29, 2!, 22 loses one revolution and rotates 1 -1= revolution clockwise in relation to the sedimentation area.

Fig. 6 shows in diagrammatic fashion the various phases or positions in the epicycloidal movement of the raking structure !8 or sediment raking arms 20, 2|, 22, a sequence of positions being marked in alphabetical order as a, b, c, d, and distinguished by showing the arms in a variety of contrasting broken lines according to the various positions. Position (1 shows the arms in full lines, the next position b shows it in short-dotted lines, position in long-dotted lines, and position d in dot and dash lines.

The practical result of this type of movement of the convolute arms or blades of the sediment raking structure is that they will reach into the corners of the settling area for the sludge, and then subsequently moving along the sides of the settling area while simultaneously retracting, they will exercise upon the sludge a bulldozing action and a relatively large quantity of sludge is effectively removed from the outer zones of the settling area and effectively conveyed towards the sludge outlet at the center. capacity of the arms or sediment conveying blades operating in this fashion is considerable, and in this respect it compares favorably with and is superior to the conventional rake arms having a series of plowing blades. mechanism, according to this invention, does not depend upon the conventional plowing efiect, but actually bulldozes the sludge inwardly, thus being able to rake from the margin to the center of the tank in /2 to /3 of a revolution of the raking arm.

From the foregoing, and especially from the above discussion of the gear ratios, it should be understood that the auxiliary scrapers 51 are effective in helping to quickly dispose of the,

sludge that accumulates towards the center of the tank, since the gear ratios mentioned above cause the auxiliary scrapers 51 to travel in counter-clockwise direction and three times as fast as the rake arms 20, 2|, 22 travel in clockwise direction. Such sludge disposal by the auxiliary scrapers tends to give a more uniform and more dewatered underfiow.

I claim:

1. In sedimentation apparatus comprising a tank having a horizontally extending bottom representing sedimentation area, a sediment collecting mechanism having a stationary vertical main axis of rotation, stationary supporting means for said mechanism and sediment outlet means in said bottom at said axis of rotation, said collecting mechanism comprising a frame structure fixed on said supporting means, a primary drive arm mounted upon said frame structure and rotatable about a stationary primary vertical axis represented by said vertical main axis, means for driving said primary drive arm, an epicycloidally rotating member representing a secondary arm mounted to rotate upon said primary arm about The sludge raking 5 In other words, the

a secondary axis that is parallel to said fixed primary axis and spaced therefrom, said epicycloidal member comprising a sediment engaging horizontally extending convolute shaped blade member, and means for driving said primary arm and said secondary arm in opposite directions and at a fixed ratio with respect to one another, said blade member thus being caused to move along epicycloidal path and to cover a cornered sedimentation area, whereby it explores the corners by moving into and out of a corner in a longitudinally slicing fashion because of a predominatingly radially directed component movement, and whereby it moves through the intervals between corners in substantially bulldozing fashion due to a predominatingly rotation-a1 component of movement, thereby positively and continuously moving sediment from the outer zone and from the corners of said sedimentation area inwardly towards said outlet means.

2. Apparatus according to claim 1, with the addition of a pier for supporting the driving means, and in which apparatus the driving means comprise a drive shaft coaxial with said vertical axis and disposed at the center of rotation of the primary arm, and gearing between the upper end portion of said shaft and said secondary arm.

3. Apparatus according to claim 1, with the addition of a pier for supporting the driving means, and in which apparatus the driving means comprise a drive shaft coaxial with said vertical axis and disposed at the center of rotation of the primary arm, secondary gearing between the upper end portion of said shaft and said secondary arm, and primary gearing effective between a lower portion of said shaft and said primary arm, said secondary gearing being disposed below the plane of rotation of said primary arm.

4. Apparatus according to claim 1, with the addition of a pier for supporting the driving means, and in which apparatus the driving means comprise a drive shaft coaxial with said vertical axis and disposed at the center of rotation of the primary arm, primary gearing between th upper end portion of said shaft and said secondary arm, and secondary gearing effective between a lower portion of said shaft and said primary arm, which latter gearing comprises a countershaft rotatably mounted in said frame structure, and is disposed below the plane of operation of said primary arm.

5. Apparatus according to claim 1, with the addition of a pier for supporting the driving means, and in which apparatus the driving means comprise a drive shaft coaxial with said vertical axis and disposed at the center of rotation of the primary arm, primary gearing between the upper end portion of said shaft and said secondary arm, and secondary gearing effective between a lower portion of said shaft and said primary arm, which secondary gearing is disposed below the plane of operation of said primary arm, with the addition that the frame structure has a fixed upwardly extending hub portion within which rotates said vertical shaft, and about which rotates said primary arm.

6. A sediment collecting mechanism according to claim 1 with the addition of a pier for supporting the driving means, and of structure fixed to and extending downwardly from said primary arm, an auxiliary sediment engaging blade means carried by said downwardly extending structure, which auxiliary blade means are disposed and effective to engage sediment conveyed to them by said convolute blade member, and to push such engaged sediment into said outlet means.

'7. in sedimentation apparatus comprising a tank having a horizontally extending bottom portion representing sedimentation area, and having sediment outlet means therein, a sediment collecting mechanism and a pier for supporting the same, said collecting mechanism comprising a frame structure mounted on said pier, a primary drive arm mounted on said frame structure and rotatable about a primary vertical axis fixed with respect to said supporting means, an epicycloidally rotating structure mounted to rotate upon said primary arm about a secondary axis that is parallel to the fixed primary axis and spaced therefrom, means for driving said primary arm and said epicycloidally rotating member in opposite directions and at a fixed ratio with respect to one another, said epicycloidally rotating member comprising a cage structure surrounding said pier, and a convolute shaped sediment engaging member provided upon and extending from the lower end portion of said cage structure, and gear means for driving said primary arm and said epicycloidally rotating member in opposite direction relative to each other, one gear as part of said gear means being fixed to the interior side of the top portion of said cage structure and constituting therewith a structural unit, said gear being concentric with the secondary axis of rotation thereof, said blade member thus being caused to move along an epicycloidal path and to cover a cornered sedimentation area, whereby it explores the corners by moving into and out of a corner in longitudinally slicing fashion due to a predomina-tingly radially directed movement, and whereby it moves through the intervals between corners in substantially transverse bulldozing fashion due to predominatingly rotational component movement, thereby positively and continuously moving sediment from the outer zones and from the corners of said sedimentation area inwardly towards said outlet means.

8. In sedimentation apparatus comprising a tank having a horizontally extending bottom portion representing sedimentation area, and sediment outlet means therein, a sediment collecting mechanism and a pier for supporting the same, saidcollecting mechanism comprising a frame structure mounted on said pier, a primary drive arm mounted on said frame structure and rotatable about a primary vertical axis with respect to said supporting means, an epicycloidally rotating structure mounted to rotate upon said primary arm about a secondary axis that is parallel to the fixed primary axis and spaced therefrom, means for driving said primary arm and said epicycloidally rotating member in opposite directions and at a fixed ratio with respect to one another, said epicycloidally rotating member comprising a cage structure surrounding said pier, three convolute shaped sediment engaging members provided upon and extending from the lower end portion of said cage structure at substantially 120 degrees interval, said sediment engaging members being mounted in such a manner that the inner end of each sediment engage ing member is connected with an intermediate portion of the preceding member, said blade members thus being caused to move along epicycloidal paths and to cover a cornered sedimentation area, whereby they explore the corners by moving into and out of a corner in longitudinally slicing fashion due to a predominatingly radially directed movement, and whereby they move through the intervals between corners in substantially transverse bulldozing fashion due to predominatingly rotational component movement, thereby positively and continuously moving sediment from the outer zones and from the corners of said sedimentation area inwardly towards said outlet means.

9. Mechanism according to claim 8 with the addition of structure fixed to and downwardly extending from said primary driv arm, and auxiliary sediment engaging blades carried by the lower end of said downwardly extending structure and disposed to operate within the confines of said cage structure and eifective to engage sediment conveyed to them by said convolute members, and to push such engaged sediment into said outlet means.

CHARLES H. SCO'I'I. 

